For many practitioners in schools and clinics, collecting data to show the effectiveness of an intervention is probably one of the most important yet challenging components of intervention implementation. This article provides practitioners with an example case study of how data can be organized and collected to determine the effectiveness of a social skills group intervention. Techniques to establish individual and group goals, determine a method to collect data, collect baseline data, and monitor progress are described. Challenges and practical strategies are discussed, and useful and specific suggestions are provided.